A data center may be defined as a location that houses computer and other electronic equipment in a high density configuration. Typically, much of the equipment is deployed in equipment racks. Densities of 128 discrete server computers per rack are achievable with current technology, and it is expected that densities will continue to increase. The servers in a rack can use considerable amounts of electricity, and accordingly, dissipate significant amounts of heat. A typical rack of servers may use 10 kW, and a large data center may have 1000 racks of servers.
To remove the heat generated in a large data center, the data center will be configured with many computer room air conditioning (CRAC) units, which operate to deliver cool air to the data center to keep servers and other devices from overheating. The energy consumed by the CRAC units comprises a significant share of the total energy consumed by the data center.